Filter for liquid crystal display device

ABSTRACT

A filter for a liquid crystal display device, having a light diffusing plate which is obtained by forming a composition in the form of a film which contains at least two photopolymerizable oligomers or monomers having refractive indexes which differ from each other by at least 0.01 and irradiating UV light on the composition. When the filter is fitted to a light emitting side of a liquid crystal display device, an angle of view of the liquid crystal display face plane is widened, shadows due to opaque parts of the device are reduced, and a Moire fringe is hardly formed.

This application is a continuation of application Ser. No. 08/432,177filed on Jun. 2, 1995, now abandoned.

FIELD OF THE INVENTION

The present invention relates to a filter for a liquid crystal displaydevice, which will widen an angle of view and suppress the decrease inpicture quality caused by opaque parts of the device, when the filter isfitted to the liquid crystal display device.

DESCRIPTION OF CONVENTIONAL ART

In these times, a liquid crystal display device is expected to be adisplay device which can compete with a cathode ray tube (CRT), becauseof its characteristics such as its thinness, light weight and highpicture quality. The modes of the liquid crystal display device which,have been developed include twisted nematic (TN) a type, a super twistednematic (STN) type, a ferroelectric type and a polymer dispersion type.Liquid crystal display devices with multicolor and high definition arecommercially sold.

With the demand for a large area display and development of ahigh-vision technique, an enlarging projection type display device isbecoming desired. In addition, with the increase of processing speed incomputers, a virtual reality display device has been developed whichdisplays an image as if it were actually present, using a liquid crystaldisplay device as a display device which is worn on a head like agoggles.

Most of the liquid crystal display devices mainly use the TN or STNaddressing mode. Such an addressing mode has a drawback in that theangle of view in which the image has satisfactory quality is narrowsince, when a displayed image is seen from an upper or lower angleand/or a right or left side angle, brightness and contrast of the imageare considerably deteriorated. This characteristic of the angle of viewhas been studied for a long time to improve it.

As one of the methods for the improvement of the above drawback, amethod for correcting a pretilt angle of the liquid crystal moleculeusing an orientation separating technique has been studied. However,since this method makes the production step complicated, a largeincrease of production cost is unavoidable.

As a simple method, there is known a method for diffusing light in awide angle range by providing a diffusing sheet on the liquid crystaldisplay panel. Since the transmission of the diffusing sheet is usually80% or less, the brightness of the liquid crystal display face plane isdecreased. The effect of enlarging the angle of view becomes larger asthe angular distribution of light to be diffused by the diffusing sheetbecomes wider. However, a currently used diffusing sheet has a narrowlight diffusing angle, and a sheet having a wide diffusing angle issought.

A liquid crystal display device based on another addressing mode isunder development, and does not exhibit commercially sufficientperformance.

In the liquid crystal display device, opaque parts such as a buselectrode or a thin film electrode (TFT) are provided around pixels. Inthe case of a display device which enlarges the image of the liquidcrystal display device such as the liquid crystal projector or thevirtual reality display device, since the opaque parts form shadows on adisplayed picture which is enlarged and projected, the image quality isconsiderably deteriorated.

To cope with this problem, Japanese Patent KOKAI Publication Nos.232460/1993 and 273540/1993 propose the provision of a phase lattice ona substrate of a transmission type liquid crystal display device, whichis on the light emitting side. This proposal suppresses the decrease ofimage quality by bending a light beam which passes through a pixel ofthe liquid crystal display device by a light diffraction effect of thephase lattice to shift the light beam to the shadow formed by the opaquepart. As the phase lattice, there are exemplified a shape modulationtype phase lattice which can be produced by a photolithography methodand a refractive index modulation type phase lattice which is preparedby distributing a monomer having a different refractive index in theresin and polymerizing. Since the phase lattice easily generates Moirefringes due to its regular structure, the accuracy during the productionof the phase lattice should be high.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a filter which canwiden an angle of view of a liquid crystal display device, and decreasethe shadow area caused by opaque parts of the device, suffers less fromthe generation of the Moire fringes when it is fitted to a lightemitting side of the liquid crystal display device, and is easilyproduced.

As a result of an extensive study, it has been found that the aboveobject is achieved by providing a filter comprising a light diffusingplate which is prepared by forming a specific photopolymerizablecomposition in the form of a film and irradiating an ultraviolet (UV)light on the film-shaped composition, and the present invention has beencompleted.

Accordingly, the present invention provides a filter for a liquidcrystal display device, comprising a light diffusing plate which isobtained by forming a composition which comprises at least twophotopolymerizable oligomers or monomers having refractive indexes whichdiffer from each other by at least 0.01 in the form of a film andirradiating a UV light on said film-shaped composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing a structure of a TFT addresseddirect vision type liquid crystal display device to which an example ofthe filter for the liquid crystal display device according to thepresent invention is fitted.

FIG. 2 is a cross sectional view showing a structure of a conventionalTFT addressed direct vision type liquid crystal display device.

FIG. 3 is a plan view of a TFT substrate

FIG. 4 is a plan view of a color filter.

FIG. 5 is a schematic view showing a method for measuring an angulardistribution of diffused light through a filter for a liquid crystaldisplay device.

FIG. 6 is a graph showing angular distributions of intensity of diffusedlight of a filter for a liquid crystal display device.

FIG. 7 is a cross sectional view showing a structure of a UV lightirradiating apparatus.

FIG. 8 is a perspective view schematically showing a UV lightirradiating apparatus.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention, at least two photopolymerizable oligomersand/or monomers are used having diffraction indexes which differ fromeach other.

Examples of combinations are two monomers include: one monomer and oneoligomer, two oligomers, and the combination obtained by further addingat least one monomer or oligomer to the combinations above.

In each combination, the difference of diffractive index between atleast two components is at least 0.01. Preferably, at least onecomponent thereof has at least two photopolymerizable functional groups.

A specific example of the combination of the photopolymerizable monomersor oligomers is the combination of at least one component selected fromthe group consisting of monomers such as 2,4,6-tribromophenyl acrylate,tribromophenoxyethyl acrylate, nonylphenoxyethyl acrylate,2-hydroxy-3-phenoxypropyl acrylate, phenylcarbitol acrylate,phenoxyethyl acrylate, etc. and oligomers such as ethyleneoxide-modified bisphenol-A diepoxy acrylate, etc., and at least onecomponent selected from the group consisting of monomers such astriethylene glycol diacrylate, polyethylene glycol diacrylate, neopentylglycol diacrylate, 1,6-hexanediol diacrylate, etc. and oligomers such aspolyol polyacrylate, modified polyol polyacrylate, polybutadieneacrylate, polyether urethane acrylate, etc.

The monomers or oligomers are not limited to the above exemplifiedcompounds. Any other photopolymerizable monomers or oligomers may beused as long as at least two monomers or oligomers to be used incombination have refractive indexes which differ from each other by 0.01or larger.

The ratio of the two photopolymerizable monomers or oligomers havingdifferent refractive indexes is in a range of from 9:1 to 1:9 in termsof a weight ratio of the higher refractive index compound to the lowerrefractive index compound.

A composition comprising the photopolymerizable monomers or oligomersaccording to the present invention preferably contains a conventionalphotopolymerization initiator to increase its curing property. Examplesof the photopolymerization initiator are benzophenone, benzil, Michler'sketones, 2-chlorothioxanthone, 2,4-dietylthioxanthone, benzoin ethylether, diethoxyacetophenone, benzyldimetylketal,2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, andso on.

To the composition comprising the photopolymerizable monomers oroligomers according to the present invention, a filler having an averageparticle size of 0.05 to 20 μm may be added in an amount of 0.01 to 5parts by weight, or a UV light absorber may be added.

As the filler, polymethyl methacrylate, polyethylene, polystyrene andsilica are exemplified.

In the present invention, the composition comprising thephotopolymerizable monomers or oligomers is formed in a film-shape, by,for example, coating the composition on a substrate or filling it in acell. Then, the UV light is irradiated on the film-shaped composition toobtain the light diffusing plate.

As a light source to be used in the photopolymerization, any lightsource may be used as long as it can emit light which contributes to thephotopolymerization. A lamp which emits a UV light beam is one ofpreferred light sources. The shape of the light source is selectedaccording to the view angle characteristics of the liquid crystaldisplay device to which the filter comprising the light diffusing plateaccording to the present invention is fitted, and the purpose of the useof the filter.

When the view angle characteristics of the liquid crystal display deviceto which the filter is fitted are insufficient in upper and lowerdirections and right and left directions of the face plane and the angleof view should be improved in all directions, or when the use of thefilter is intended to decrease the shadows caused by the opaque parts ofthe liquid crystal display device, preferably the light is diffusedequally in all directions by the light diffusing plate. In such a case,as when the UV light is to be irradiated in the photopolymerizationstep, parallel light rays such as sun light are most preferably used,while a spherical or box-shaped light source or a rod-shaped lightsource having a ratio of a long axis to a short axis of 2:1 or less mayprovide the same performance.

When the view angle characteristics of the liquid crystal display deviceto which the filter is fitted are sufficient in the right and leftdirections but insufficient in the upper and lower directions of theface plane and the angle of view should be improved in the upper andlower directions, the light is diffused preferably in the upper andlower directions by the light diffusing plate, in view of the effectiveutilization of the emitted light from the liquid crystal display device.In such a case, when the UV light is irradiated from a linear orrod-shaped light source to photopolymerize and cure the film-shapedcomposition, a filter comprising a light diffusing plate withdirectional properties of light diffusion can be obtained. The angle ofview can be widened by arranging the light diffusing direction of thefilter in a direction in which the angle of view of the liquid crystaldisplay device is desired to be improved.

A selective diffusing property of the light diffusing plate in relationto the incident angle of light is defined by a haze of the plate inrelation to the incident angle of light. Preferably, the light diffusingplate used in the present invention has a property of changing the hazedepending on the incident angle of light, and both a light incidentangle range with a light diffusing ability of a haze of at least 30% (adiffusing angle range) and other light incident angle range without alight diffusing ability. When the maximum haze in the diffusing anglerange is less than 30%, an effect of enlarging the angle of view isinsufficient. When this maximum haze exceeds 85 %, the image may blur.Then, the maximum haze of the light diffusing plate is preferably in therange between 30% and 85%.

The thickness of the filter comprising the light diffusing plate of thepresent invention is not limited. To achieve the light diffusingability, the thickness of the filter is at least 10 μm, preferably from50 to 300 μm.

The filter comprising the light diffusing plate of the present inventionis produced by utilizing a property of the composition comprising thespecific photopolymerizable monomers or oligomers that they arephotopolymerized and cured while causing a phase separation by theirradiation of the UV light. This method can produce the filtercomprising a refractive index modulating type smooth light diffusingplate having a domain gap of 1 to 20 μm, without the use of a maskduring the UV light irradiation. Since the separated phases have acontinuous interface between them, no light is reflected at theinterface when light passes through the obtained filter, so that thelight transmission is not decreased. Since this filter does not have astructure with regularity unlike the phase lattice, it does not form anyMoire fringe. In addition, the production step uses no mask but includesonly the UV light irradiation on the film-form composition, theproduction process is simple and suitable for mass production.

When the filter comprising the light diffusing plate of the presentinvention is fitted to the light emitting side of the liquid crystaldisplay device, it is preferably assembled in a laminate by inserting itbetween the outer surface of the device and a transparent substrate.

As the transparent substrate to be used in the laminate, any transparentsubstrate can be used. Examples are polycarbonate resins, methacrylicresins, polyethylene terephthalate (PET) resins, polystyrene resins, ortransparent glass. An outer surface of the transparent substrate may betreated by at least one treating method selected from low reflectingtreatment, glare proofing treatment and hard coat treatment. A methodfor laminating the transparent substrate and the light diffusing plateis not limited, and may be any of conventional methods.

When the filter comprising the light diffusing plate is fitted to thelight emitting side of the liquid crystal display device, preferably itis contacted to the face plane as closely as possible. In this step, apolarizing plate which is used outside the liquid crystal panel can beintegrated with the light diffusing plate to adhere the light diffusingplate directly to the liquid crystal display device.

As the liquid crystal used in the liquid crystal display device to whichthe filter comprising the light diffusing plate of the present inventionis preferably fitted, and an addressing system of the device, any systemsuch as a passive-matrix-addressed system using TN and STN liquidcrystals, and a TFT type active-matrix-addressed system using a TNliquid crystal may be used.

As an example, FIG. 2 shows a structure of a TFT addressed direct visiontype liquid crystal display device. In the case of the direct visiontype liquid crystal display device, a light beam emitted from a backlight 1 passes through a polarizing plate 2, a TFT substrate 3, a liquidcrystal cell 4, a color filter 5, a counter substrate 6 and a polarizingplate 7 and reaches eyes of a viewer. In the case of the TFT addressedliquid crystal display device, a TN mode is often used. In the TN mode,since a twisting angle of the liquid crystal is 90 degrees, an angle ofview is only about 60 degrees.

FIG. 3 shows an example of a TFT substrate. On the TFT substrate, TFTdevices 8, source bus electrode 9 which supply a voltage to the TFTdevices, and gate bus electrodes 10 are arranged. In FIG. 3, 11 standsfor a pixel electrode.

FIG. 4 shows an example of a color filter. On the color filter, pixels12 which develop a color on the liquid crystal display device, and ashielding part 13 (black matrix) which prevents light leakage betweenthe pixels and suppresses reflection of external light on the TFTdevices and the bus electrodes are patterned. Then, the light beamemitted from the back light is intercepted by the opaque parts such asthe TFT devices 8, the bus electrodes 9, 10, the shielding part 13, andthe like, whereby the image is roughened.

FIG. 1 shows a structure of a direct vision type liquid crystal displaydevice, in which a filter 14 comprising the light diffusing plate of thepresent invention is fitted to a light emitting side of the polarizingplate 7 present on the viewer side.

In the case of a liquid crystal projector, a light source lamp is usedin place of the back light 1 of FIG. 1 and a projector screen is placedat a position of the viewer.

EXAMPLES

The present invention will be illustrated by the following Examples,which do not limit the scope of the present invention in any way.

The upper and lower direction angles used in the Examples are intendedto mean upper and lower direction angles, respectively from a normalline to a face plane of a liquid crystal television set used in theExamples.

In the Examples, "parts" are by weight.

Example 1

To a polyether urethane acrylate having an average molecular weight ofabout 6000 (a refractive index of 1.460) (40 parts) which was obtainedby the reaction of polypropylene glycol, hexamethylene diisocyanate and2-hydroxyethyl acrylate, 2,4,6-tribromophenyl acrylate (a refractiveindex of 1.576) (30 parts), 2-hydroxy-3-phenoxypropyl acrylate (arefractive index of 1.526) (30 parts), and2-hydroxy-2-methylpropiophenone (1.5 parts) as a photopolymerizationinitiator were added and mixed to prepare a photopolymerizablecomposition.

The composition was coated on a glass plate to a thickness of about 130μm to form a film-form photopolymerizable composition. This film and theglass plate were passed through a conveyor type UV light irradiatingapparatus having a lamp aperture of 5 cm×5 cm, a lamp power of 120 W/cm,and a conveyor speed of 0.4 m/min. to photopolymerize the composition.Thereby, a filter comprising a light diffusing plate for a liquidcrystal display device was produced.

An angular distribution of light intensity diffused by the filter forthe liquid crystal display device was measured with an apparatus formeasuring an angular distribution of diffused light intensity(manufactured by Shimadzu Corporation). FIG. 5 schematically shows thisapparatus. A light beam 20, which is irradiated on the filter 14 for theliquid crystal display device at an incident angle 23 (θ) from a normalline direction to the filter 14, is diffused by the filter 14 andemitted at an angle 24 (φ). When the angular distribution of thediffused light 21 is measured by a light intensity detector 19, thelight diffusion characteristics of the filter for the liquid crystaldisplay device is measured.

FIG. 6 shows the light diffusion characteristics when light of 550 nmwas irradiated on the filter for the liquid crystal display deviceaccording to the present invention. The distribution curves 15 to 18 arethe intensity distributions of diffused light at incident angles of 0,5, 10 and 15 degrees, respectively.

The diffusion angle φ is 0 degree on a direction 22 of a light beamwhich propagates straight in relation to the incident light, andregarded as a positive angle when the light beam is emitted on a sideincluding the normal line.

The incident light in the normal line direction to the filter for theliquid crystal display device provides an angular distribution of thediffused light intensity which is an Gaussian distribution having a halfwidth of about 8 degrees, as shown by the distribution curve 15. Incontrast, the incident light irradiated from a direction at an angle of15 degree from the normal line provides the angular distribution of thediffused light intensity having the maximum around 27 degrees of thediffusion angle. In other words, the incident light irradiated from adirection at an angle of 15 degrees from the normal line is diffused byabout 27 degrees by the filter 14 for the liquid crystal display device.

In FIG. 1 showing the structure of the direct vision type liquid crystaldisplay device to which the filter 14 comprising the light diffusingplate of the present invention is fitted, the light beam which passesthrough the polarizing plate 7 on the light emitting side is bent on thewider angle side when it passes through the filter 14 for the liquidcrystal display device. The light beam emitted from the liquid crystaldisplay device has a higher contrast as it is closer to the normal linedirection to the liquid crystal display device. Then, as the emittedlight near the normal line direction is diffused on the wider angleside, the contrast on the wider angle side is improved. When the emittedlight is diffused, a light beam reaches the shadow areas caused by theopaque parts of the liquid crystal display device and makes the shadowimperceptible, whereby the image quality is improved.

In the case of the liquid crystal projector, the light source lamp unitis placed instead of the back light 1 in FIG. 1 and the projectionscreen is placed at the position of the viewer, whereby it is possibleto decrease the shadow areas caused by the opaque parts. In this case,the light beam reaches the shadow areas caused by the opaque parts ofthe device and illuminates those areas by the light diffused by thefilter for the liquid crystal display device, whereby the image qualityis improved, as in the case of the direct vision liquid crystal displaydevice.

Comparative Example

As a liquid crystal display device, a liquid crystal color TV set 4E-L1manufactured by Sharp Corporation was used. Using a digital patterngenerator MTSG-1000 manufacture by Sony Corporation, a window patternwas imaged on the face plane, and a white luminance in the white windowand a black luminance in the black window were measured from the upperdirection angle of 50 degrees to the lower direction angle of 60 degreeswith a luminance meter LS-100 manufactured by Minolta Co., Ltd.

The maximum white luminance was 128.6 nt at the lower direction angle of15 degrees. An angle of view in relation to the luminance was defined asan angle range in which the luminance was at least one third (1/3) ofthe maximum white luminance, that is, at least 42.9 nt. An angle of viewin relation to the contrast was defined as an angle range in which aratio of white luminance to black luminance was at least 5:1. Then, anangle range in which both the luminance and the contrast were satisfiedwas defined as an angle of view of the face plane of the liquid crystalTV set. The result is shown in Table 1.

Example 2

As a resinous composition for the light diffusing plate, there was useda photopolymerizable composition (40 parts) prepared by mixing apolyether urethane acrylate having an average molecular weight of about6000 which was obtained by the reaction of polypropylene glycol,hexamethylene diisocyanate and 2-hydroxyethyl acrylate,2,4,6-tribromophenyl acrylate (30 parts), 2-hydroxy-3-phenoxypropylacrylate (30 parts), and 2-hydroxy-2-methylpropiophenone (1.5 parts) asa photopolymerization initiator.

The resinous composition was coated on a PET film having a thickness of188 μm and irradiated with a UV light at an irradiation angle of 17degrees using an apparatus shown in FIGS. 7 and 8, to obtain a lightdiffusing plate having a thickness of 205 μm. In FIGS. 7 and 8, 25stands for a rod-shape high pressure mercury lamp of 80 W/cm, 26 standsfor a light shielding plate, 27 stands for a conveyor, 28 stands for thePET film having the thickness of 188 μm on which the resinouscomposition was coated, and 29 stands for the irradiation angle of theUV light used in this Example.

The maximum haze of the light diffusing plate and a diffusion anglerange which was defined by the haze of at least 30% are shown in Table2.

This light diffusing plate was fitted to the face plane of the liquidcrystal TV set as used in the Comparative Example with arranging thelight diffusion angle range in the lower direction angle range, and thesame measurement as in the Comparative Example was carried out. Theresult are shown in Table 1.

Example 3

A light diffusing plate having a thickness of 205 μm was produced fromthe same resinous composition for the light diffusing plate as used inExample 2 by irradiating the composition at an irradiation angle of 22degrees with the apparatus shown in FIGS. 7 and 8.

The maximum haze of the light diffusing plate and a diffusion anglerange which was defined by the haze of at least 30% are shown in Table2.

This light diffusing plate was fitted to the face plane of the liquidcrystal TV set as used in the Comparative Example with arranging thelight diffusion angle range in the lower direction angle range, and thesame measurement as in the Comparative Example was carried out. Theresult are shown in Table 1.

Example 4

A light diffusing plate having a thickness of 205 μm was produced fromthe same resinous composition for the light diffusing plate as used inExample 2 by irradiating the composition at an irradiation angle of 27degrees with the apparatus shown in FIGS. 7 and 8.

The maximum haze of the light diffusing plate and a diffusion anglerange which was defined by the haze of at least 30% are shown in Table2.

This light diffusing plate was fitted to the face plane of the liquidcrystal TV set as used in the Comparative Example with arranging thelight diffusion angle range in the lower direction angle range, and thesame measurement as in the Comparative Example was carried out. Theresult are shown in Table 1.

Example 5

A light diffusing plate having a thickness of 205 μm was produced fromthe same resinous composition for the light diffusing plate as used inExample 2 by irradiating the composition at an irradiation angle of 31degrees with the apparatus shown in FIGS. 7 and 8.

The maximum haze of the light diffusing plate and a diffusion anglerange which was defined by the haze of at least 30% are shown in Table2.

This light diffusing plate was fitted to the face plane of the liquidcrystal TV set as used in the Comparative Example with arranging thelight diffusion angle range in the lower direction angle range, and thesame measurement as in the Comparative Example was carried out. Theresult are shown in Table 1.

Example 6

The light diffusing plate which was produced in Example 2 was fitted tothe face plane of the liquid crystal TV set as used in the ComparativeExample with arranging the light diffusion angle range in the upperdirection angle range, and the same measurement as in the ComparativeExample was carried out. The result are shown in Table 1.

Example 7

The light diffusing plate which was produced in Example 3 was fitted tothe face plane of the liquid crystal TV set as used in the ComparativeExample with arranging the light diffusion angle range in the upperdirection angle range, and the same measurement as in the ComparativeExample was carried out. The result are shown in Table 1.

Example 8

The light diffusing plate which was produced in Example 4 was fitted tothe face plane of the liquid crystal TV set as used in the ComparativeExample with arranging the light diffusion angle range in the upperdirection angle range, and the same measurement as in the ComparativeExample was carried out. The result are shown in Table 1.

Example 9

The light diffusing plate which was produced in Example 5 was fitted tothe face plane of the liquid crystal TV set as used in the ComparativeExample with arranging the light diffusion angle range in the lowerdirection angle range, further the light diffusing plate which wasproduced in Example 4 was fitted over the above light diffusing platewith arranging the light diffusion angle range in the upper directionangle range, and the same measurement as in the Comparative Example wascarried out. The result are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                Angle of view                                                                 Upper direc-                                                                            Lower direc-                                                                             Range of                                                 tion angle                                                                              tion angle angle of view                                    ______________________________________                                        Comp. Ex. 32 degrees  33 degrees 65 degrees                                   Example 2 31 degrees  41 degrees 72 degrees                                   Example 3 32 degrees  43 degrees 75 degrees                                   Example 4 32 degrees  52 degrees 84 degrees                                   Exampie 5 32 degrees  55 degrees 87 degrees                                   Example 6 34 degrees  34 degrees 68 degrees                                   Example 7 37 degrees  34 degrees 71 degrees                                   Example 8 40 degrees  33 degrees 73 degrees                                   Example 9 40 degrees  55 degrees 95 degrees                                   ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                                 Maximum      Diffusion                                                        haze         angle range                                             ______________________________________                                        Example 2  75%             6 to 40 degrees                                    Example 3  74%            10 to 44 degrees                                    Example 4  75%            15 to 49 degrees                                    Example 5  75%            20 to 54 degrees                                    ______________________________________                                    

EFFECTS OF THE INVENTION

When the filter comprising the light diffusing plate of the presentinvention is used, the angle of view of the liquid crystal display faceplane is widened, the shadows due to the opaque parts are reduced, andthe Moire fringe is hardly formed. The light diffusing plate of thepresent invention is easily produced.

What is claimed is:
 1. A method for widening a view angle of a liquidcrystal display device comprising fitting a filter to a liquid crystaldisplay device, wherein said filter comprises a light diffusing platewhich is obtained by shaping into a film a composition comprising atleast two photopolymerizable oligomers or monomers having refractiveindexes which differ by at least 0.01 and irradiating ultraviolet lighton said film of the composition, wherein the polymerizable oligomers ormonomers have acrylate functional groups.
 2. The method according toclaim 1, wherein said light diffusing plate has a domain gap of 1 to 20μm.
 3. The method according to claim 1, wherein said ultraviolet lightis irradiated from a light source selected from the group consisting ofa spherical light source, a box-shaped light source and a rod-shapedlight source having a ratio of a long axis to a short axis of 2:1 orless.
 4. The method according to claim 1, wherein said light diffusingplate has both a light incident angle range with a light diffusingability for achieving a haze of at least 30% and a light incident anglerange without a light diffusing ability.
 5. The method according toclaim 4, wherein said light diffusing plate is obtained by theirradiation of ultraviolet light from a linear or rod-shaped lightsource.
 6. The method according to claim 4, wherein the maximum haze inthe incident angle range in which the light diffusing plate has lightdiffusing ability is from 30 to 85%.
 7. The method according to claim 4,wherein said light diffusing plate has a domain gap of 1 to 20 μm. 8.The method according to claim 4, wherein said filter has a thickness ofbetween 10 and 300 μm.
 9. The method according to claim 4, wherein thecombination of the photopolymerizable monomers or oligomers is acombination of at least one component selected from the group consistingof 2,4,6-tribromophenyl acrylate, tribromophenoxyethyl acrylate,nonylphenoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate,phenylcarbitol acrylate, phenoxyethyl acrylate, and ethyleneoxide-modified bisphenol-A diepoxy acrylate; and at least one componentselected from the group consisting of triethylene glycol diacrylate,polyethylene glycol diacrylate, neopentyl glycol diacrylate,1,6-hexanediol diacrylate, polyol polyacrylate, modified polyolpolyacrylate, polybutadiene acrylate, and polyether urethane acrylate.10. The method according to claim 4, wherein the two photopolymerizableoligomers or monomers having different refractive indexes are present ina weight ratio of from 9:1 to 1:9.
 11. The method according to claim 1,wherein said filter has a thickness of between 10 and 300 μm.
 12. Themethod according to claim 1, wherein the combination of thephotopolymerizable monomers or oligomers is a combination of at leastone component selected from the group consisting of 2,4,6-tribromophenylacrylate, tribromophenoxyethyl acrylate, nonylphenoxyethyl acrylate,2-hydroxy-3-phenoxypropyl acrylate, phenylcarbitol acrylate,phenoxyethyl acrylate, and ethylene oxide-modified bisphenol-A diepoxyacrylate; and at least one component selected from the group consistingof triethylene glycol diacrylate, polyethylene glycol diacrylate,neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, polyolpolyacrylate, modified polyol polyacrylate, polybutadiene acrylate, andpolyether urethane acrylate.
 13. The method according to claim 1,wherein the two photopolymerizable oligomers or monomers havingdifferent refractive indexes are present in a weight ratio of from 9:1to 1:9.